Beetles (Coleoptera) are one of the main groups of insects. They are the most speciose order in the entire animal kingdom, followed closely by the butterflies, bees and wasps, and flies. 40 % of all animal species are beetles, and every day new species are discovered.

The forewings of beetles are transformed into hard shells, called elytra. These elytra form an armour protecting the abdomen and the sensitive hindwings. The forewings are not used (at least not actively flapped) in flying, but they must (in most species) be raised in order to move the hindwings. After landing the hindwings are folded below the elytra. Most beetles can fly, but few reach the dexterity of some other groups, e.g. flies, and many species only fly if absolutely necessary. Some beetles have elytra that have grown together and cannot fly at all; a few have lost their wings altogether.

Beetles can be found in almost all biotopes. They don't occur in the sea or in the polar regions.